Bottom hole igniter and burner



April 29, 1958 c. E. FORD BOTTOM HOLE IGNITER AND BURNER Filed Aug. 27, 1954 INVENTOR CLARENCE E. FORD United States Patent BOTTOM HOLE IGNITER AND BURNER Clarence E. Ford, Tulsa, Okla., assignor to Sinclair Oil 8; Gas Company, Tulsa, Okla, a corporation of Maine Application August 27, 1954, Serial No. 452,565

1 Claim. (Cl. 166-59) This invention relates to an apparatus for producing high temperatures in subterranean passages by combustion of a fuel such as oil or gas. More particularly, this invention relates to a bottom-hole igniter and burner which can be lowered into subterranean passages, such as oil, shale or water wells, and while in this position ignite and burn a fuel, passed from the earths surface to produce high temperatures in the wells.

It is generally recognized that a large percentage of the oil in the average oil reservoir cannot be recovered by ordinary recovery methods. to the decrease in difierential pressure between the reservoir sands and the well bore, and in part is the result of greater average viscosity of reservoir oil after removal of the less viscous oil in addition to clogging of the formations resulting from various sediments, such as insoluble inorganic materials and waxy hydrocarbons, which build up in the formations in the paths of the oil to the well bore.

Recent research has shown the feasibility of improving the percentage recovery of oil or other fluids from underground reservoirs by the institution and propagation of an underground heat wave in the reservoir sands (see paper 348-G by Grant et al., before the February 14 to 18, 1954 meeting of AIMME, entitled Development of an Underground Heat Wave for Oil Recovery). In addition to the method described in the Grant et al. paper, other methods such as merely heating sands around a solubilizing the deposits restricting flow.

The present invention comprehends an igniter and burner for establishing a high temperature heated zone in subterranean passages to facilitate increased percentage recovery of fluids from underground reservoirs. My device is adapted to have small physical dimensions and is capable of insertion into well strings of small diameter cement lined tubing, which have been used for water injection and which have become sludged or clogged with foreign agents, to provide heated zones in such tubing. The heat and flame provided by my apparatus elfect a burning and disintegration of the foreign agents which may consist of bacterial organisms, insoluble carbonates, or heavy waxy hydrocarbons. After this treatment, they can be blown from the Well by air or flushed to the surface by water. The design of my device provides uniform and adequate heat transfer surface in order to raise fuel from ambient to auto-ignition temperatures and to maintain the ignition temperature during continuous fuel feed, and is characterized by providing maximum heating surface and maximum heat transfer area for a minimum diameter igniter and burner.

The apparatus constituting my invention can be readily understood by reference to the attached vertical cross section drawing of my bottom hole igniter and burner which is suitable for the above and other purposes.

The igniter and burner apparatus comprises an elongated thin-walled sheath heating element constructed of electrically conducting material, such as wound resistance This is due generally borehole bottom can aid in the recovery by melting or 2,8314 1 7 Patented Apr. 29,1958

wire or carbon, defining tube member 1 having a tubular coil 2 helically disposed about a substantial portion of its length and electrically insulated therefrom preferably with a material having a high thermal conducting factor. At its upper end, tube member 1 is soldered or otherwise joined to a second tube member 14, constructed of an electrically conducting metal such as steel, which extends upwardly and has a threaded end 13, or similar means so that it can be connected to a fuel pipe or string of metallic well tubing 6 which in turn extends to the surface of the earth. Check valve means 16 and fuel screen 7 can be provided in the second tube member 14 to provide for screening the fuel and effecting control of its flow. Tube member 1 is closed at its lower end by an electrically conducting end member 5 in contact with the walls of tube member 1. At its upper-most end the tubular coil 2 disposed about tube member 1 communicates with a fuel supply line 11 which extends upwardly along the side of second tube member 14 and communicates with fuel pipe or well tubing 6. The cross sectional area of the tubular coil 2 is, preferably, smaller than the cross sectional area of fuel line 11 or fuel pipe 6; this feature provides an increase in the velocity of the fuel in the area about the heating elements to enhance the heat transfer characteristic of my burner and igniter.

Centrally disposed in tube member 1 is a resistance element 4 in electrical contact with the tube member 1 at the end plate 5. At its upper end the resistance element 4, which is constructed of a suitable Nichrome wire or similar electrical resistance material, is soldered or otherwise joined to an insulated conductor 3 which, in turn, extends upwardly through second tube member 14 and then alongside of fuel pipe 6 to the surface of the earth. At the point of entry of the resistance element 4 into sheath-like member 1 the resistance element is desirably maintained in spaced relationship with the walls of tube member 1 by an insulating spacer disk 15; the spacer disk 15 performs the additional function of being the upper closure member for tube member 1 and hence aids in preventing heating values from escaping upwardly away from the fuel igniting and burning space.

A casing member 12, constructed of steel or other strong material, is provided about the part of the apparatus including resistance element 4, the tube member 1 and the helical coil 2 for the purposes of supporting and protecting the described elements from damage due, for example, to abrasion from lined tubing strings. Generally, the casing is open at its lower end; it can, however, contain an end member (not shown) adapted to permit an extension of helical coil 2 to pass through. The casing can be welded to second tube member 14 at points alongits length to permanently fix it about the burner area. In operation a thermocouple (not shown) can be attached alongside of the burner by suitable clips to provide a method of observing the temperatures in the burner area.

The path of fuel in my novel apparatus is into the fuel pipe 6 through fuel supply line 11 and then into the helical coil 2 disposed about the heating elements. The hot fuel issues from the lower end of coil 2 and flashes into air or other source of oxygen supplied from the surface through the annular space between fuel tube 6 and well casing or tubing string as the case may be. The combustion products enter the reservoir formation or issue into well lining elements below the burner and then enter the formation through suitable perforations in the well lining (not shown). The electrical circuit defined by the elements of my apparatus is through insulated conductor 3, into resistance element 4, into plate member 5, through sheath-like tube member 1 which is grounded to second tube member 14 and then through fuel pipe 6 to return to the surface.

In operation, my bottom-hole igniter and burner is at- 1 tached to the end of a string of Well tubing and lowered into the passage, e.g., an oil well; the insulated conductor extends from the igniter to the earths surface. After appropriate surface connections and seals have been made, current is applied and the burner is permitted to heat to operating temperature, i. e., about 500 to 1500 F. Oil, or other suitable fuel mixture, is passed into fuel pipe 6 downwardly to the igniter and burner area into the helical coil where it is raised to auto-ignition temperature by the heat from the heating and resistance elements, and then flashes into air supplied from the surface. The hot combustion products produced at the lower end of the helical coil issue into the surrounding strata, repressuring the area and raising the temperature of the strata and materials contained therein. Continned operation of the apparatus can produce a heat wave extending outwardly through the fluid-containing formation and thereby drive the fluids towards specially drilled output wells. Where the effect desired is viscosity lowering of the fluids, or a melting and solubilizing effect on sediments, intermittent operation of the apparatus can be suficient.

In constructing the bottom-hole igniter and burner, its length and diameter will be a matter depending upon the conditions to be observed. For instance, the length is sufiicient to heat the fuel mixture from ambient to auto-ignition temperatures and the diameter sufficiently small to fit the passage in which it is to be employed. It can be seen that my invention thus provides a compact, efficient, rapid and inexpensive means for initiating and maintaining combustion in subterranean passages. The novel relationship of the heating element, resistance element and helical fuel coil provides maximum heating surface and heat transfer areas for minimum diameter in a burner and igniter apparatus.

I claim:

A bottom hole igniter and burner for initiating com- ,4. bustion in subterranean passages which includes an electrically conductive elongated fuel conduit for lowering into a subterranean passage, an electrically conductive elongated thin-walled tube closed at each end to define a closed chamber, said tube being supported at one end thereof to an end of said conduit in electrical connection therewith, a tubular coil helically disposed about and electrically insulated from said tube, means communicating the interior of said conduit With the interior of said coil at the end thereof adjacent said one end of said tube, the other end of said coil being open to said subterranean passage, an elongated electrical resistance element centrally disposed in said closed chamber electrically insulated from the walls of said tube and said one end thereof and electrically connected to the other end thereof remote from said conduit, conductor means electrically insulated from said tube and conduit electrically connected to said resistance element whereby said conductor means, said resistance element, said tube and said conduit are electrically connected in series for connection to an external electrical power source, and a protective sheath enclosing said coil and tube and supported by said one end of said conduit.

References Cited in the file of this patent UNITED STATES PATENTS 1,457,479 Wolcott June 5, 1923 1,651,450 Farrington Dec. 6, 1927 1,764,213 Knox June 17, 1930 2,048,104 Clinefelter July 21, 1936 2,332,708 Freeman Oct. 26, 1943 2,408,673 Moorehead Oct. 1, 1946 2,444,756 Steffen July 6, 1948 2,506,853 Berg et al. May 9, 1950 2,673,919 Arvins et a1 Mar. 30, 1954 2,722,278 Kaasa Nov. 1, 1955 

